Fuse device



Jan. 9, 1940. G. B. CURRIE FUSE DEVICE Filed March 2, 1938 lI\\ 'ENTOR.

ATTORNEY.

Patented Jan. 9, 1940 PATENT OFFICE FUSE DEVICE George B. Currie, Detroit, Mich., assignor of onehalf to Leonard E. Brown, Detroit, Mich.

Application March 2,

3 Claims.

This invention relates to fuses or fuse assemblies of the plug type as used for the protection of electric equipment against overloading, and has for its object to render practically impossible the abuses at present generally prevalent of substituting plug fuses of higher capacity where those of lower capacity are indicated, or of inserting coins, wire or other shorting means in the fuseholders or adapters.

To such an end, more or less elaborate fuse organisations or assemblies have from time to time been suggested which called for more expensive or complicated devices than those which are in common use and have become to a very great extent standardized, and such prior suggestions further do not readily lend themselves to incorporation in the standard fuseholders already installed by the millions throughout this country alone. To replace such existing fuseholders for the purpose of substituting special fuseholders for use with nontamperable fuse plugs would en tail vast expense, and it is a primary object of the present invention to provide means for readily converting'the ordinary standard type of fuse holder into a nontamperable type and to provide a cooperating nontamperable plug fuse requiring no additional parts to be added to the ordinary standard plug, and only the slightest change in the form of the plug itself amounting to the provision of a recess which can be formed in the molding without any additional operation or expense being necessarily added to its production.

Still further objects and advantages subsidiary to the aforesaid objects, or resulting from the invention as it may be carried into effect, will become apparent as the said invention is carried into effect.

In carrying the said invention into effect, I may provide a standard fuseholder or base, comprising a socket member of porcelain or other insulating material enclosing a threaded metal shell connected to one conductor and a second conductor insulated from said shell and presenting a contact in the form of a screw substantially in the center of the base of the socket in the manner well. known in the art, with a button or adapter of insulating material having a more or less central orifice through which the stem of the aforesaid screw maybe passed to secure the button to the second conductor and in position in the base of the socket. The button has an upstanding tubular wall isolating the head of the screw from. the shell and preferably spaced from and approaching the height of the shell, and a the plug for use with the so converted socket is 1938, Serial No. 193,466

provided with a groove or recess in its socketentering end in counterpart to the upstanding wall of said button. Thus variations in the dimensions of the said wall, which are intended to be related to the capacity of the fuse to beused, 5 must be met by corresponding variations in the dimensions of the groove in the fuse, and the presence of the said wall will preclude or render very diflicult the successful shorting of the contacts by inserting a coin, wire or the like.

All of which is more particularly described and ascertained in and by the following description, by way of example, of the accompanying drawing, wherein: I

Figure 1 is a cross sectional view through the socket of a common standard fuseholder or base showing in dotted lines a standard plug fuse in one of the sockets, and in full lines and in section the improved nontamperable fuse plug and its adapter or button positioned in the other of the sockets;

Figure 2 is a detail sectional view taken through one of the sockets and the nontamperable fuse plug on a plane indicated by the line 2-2 in Figure. 1;

Figure 3 is a plan of the button or adapter removed;

Figure 4 is a plan of underside of the improved fuse plug;

Figure 5 is a cross sectional view similar to the right-hand portion of Figure 1, illustrating a slightly modified arrangement of the parts applied to another but not so common form of fuseholder;

Figure 6 is a fragmentary sectional detail view of the button securing means of Figure 5; and

Figure 7 illustrates a slightly modified form of the arrangement of Figure 5, wherein one of the conductors enters above the flange of the button or adapter.

Similar characters of reference indicate similar parts in the several figures of the drawing.

3 indicates the porcelain body of a fuse block or holder having upstanding socket members 4 formed thereon which house threaded metal shells 5 connected to conductors 6 forming one of the fuse block contacts, the other contact in each case being inv the form of the centrally located screw 1, suitably insulated from the first contact as by the insulating disk or washer 8 and connected to the conductor 9, all of which is common knowledge in this art.

It is well known in common practice that the ordinary type of fuse block Ill may be readily removed and substituted for other plugs, of highbottom of the socket and provided with a central hole l3 through which the same screw "5, which formed the center contact and held the insulating washer 8 in place, may be passed to secure the button or adapter in position in the socket, the said button or adapter having provided on its upper surface air-upstanding tubular portion l4 surrounding the head of the said screw i and providing an annular isolation of the same from the shell 5.

Instead of the ordinary standard fuse plug it,

I provide a plug I5 which may be the same in all respects except that the body 18 thereof is pro- Vided with an annular coaxial recess or groove i1 extending inwardly of the entering end of the said plug and formed in counterpart of the upstanding tubular wall Id of the button if, the provision of this groove thereby forming a. stem or projection i8 corresponding to the bore of the tubular wall M of the said button. This stem carries the central fuse contact 69 from which the fuse 20 extends in the usual manner to the threaded metal sheath 2! of the plug which engagesthe shell 5 of the socket when .the fuse plug is entered thereinto in the well known manner.

Obviously if the stem I3 of the plug is larger than the bore of the button or adapter, or the outside diameter of the said wall M greater than that of-the groove IT, or if the height of the wall 14 be greater than the'depth of the said groove ll, the fuse plug could not be inserted in a manner to establish a closed circuit there'through. It will also be apparent that the presence of the upstanding wall of the button prevents the laying of acoin or other conductor across the contacts of the fuse block within the socket, and that, by

to is shown, wherein the screw '1 is off center relative to the socket, and the button or adapter llis somewhat undercut as at 22, to provide clearance for the head of the said screw 1'. A metal eyelet. 23 is provided through which a screw 2 may be passed to secure the button, or adapter in position in the socket and also to establish an electrical connection through the said eyelet between the base of the Shelli and the conductor 6 which in this case happens .-to be beneath the base of the block.

The fuseholder shown in these Figures 5 and 6' is also of a standard type although not in such extensive use as that previously described. This type of fuse holder is also sometimes modified bythe provision of an opening 25 in the said shell through which opening conductor 6 is passed and secured to the upper surface of the base, and in this case it simply engages the said conductor 6 between the head of the screw 24 and the flange of the adapter ll whereby electrical connection with the base of the shell 5 is again established through the said eyelet 23.

After the securing in position in the socket of the button or adapter, the head of the securing screw 1 or 24 may be mutilated, filed smooth, or otherwise threaded to render difficult its removal, or of course the screw head may be of any of the well known forms requiring a special tool for that purpose, as will be well understood.

' This invention may be developed within the scope of thefollowing claims without departing from the essential features of the said invention and it is desired that the specification and drawing be read as being merely illustrative and not in a limiting sense, except as necessitated by the prior art.

. What I claim is: I

1. In combinationwith a standard fuse block, comprising a socket enclosing a screw shell contact and a center contact in the form of a screw in the base of said socket; a fuse plug having threaded engagement with said shell, said plug also having a center contact in its entering end, andmeans rendering said standard block nontamperable, said means being a nonconducting adapter engaged and held in position by said center screw contact, the confronting faces of said adapter and said plug having complementalintel-fitting formations capable of dimensional lim" itations to prevent substitution of a higher rated fuse that that for which the adapter is designed.

2. In combination with a standard fuse block, comprising a socket enclosing a screw shell con-' tact and a center contact in the form of a screw in the base of said socket; a fuse plug-having threaded engagement with said shell, said plug also having a center contact in its entering end, and means rendering said standard block nontamperable, said. means being a nonconducting adapter engaged and held in position by said center screw contact, said adapter having an upstanding .wall about said center screw contact and extending substantially to the height of said shell, the confronting face of said plug being recessed complementary to said upstanding wall, whereby the center contact of said plug may be passed within said wall to meet the center contact of said block.

3. In combinationwith a standard fuse block, comprising a socket enclosing a screw shell contact and a center contact in the form of a screw in the base of said socket; a fuse plug having threaded engagement with said shell, said plug also having a center contact in its entering end, and means rendering said standard block non tamperable, said means being a nonconducting adapter engaged and held in position by said center screw contact, the confronting faces of said adapter and said plug having complementary interfitting formations capable of dimensional limitations proportioned to prevent the entrance into the outer shell of a higher rated fuse than that for which the adapter is designed.

GEORGE B. CURRIE. 

